The present disclosure relates to industrial equipment comprising different units selectively attachable to each other to jointly perform a desired activity. More specifically, the present disclosure relates to industrial equipment where communications signals and/or power must be transferred between such different units in order to perform the activity desired.
One example of such equipment is a lift truck carriage that is selectively attachable to a load handler to lift and move cargo, such as crates, paper rolls, etc. from one place to another. Typically, the load handler will include load-engaging members such as forks that raise pallets, clamps that grasp paper rolls, etc. where positioning of the load-engaging members as well as movement of the load is accomplished hydraulically using fluid supplied from a reservoir on the lift truck. Movement of pressurized fluid between the lift truck and the load handler typically occurs in hydraulic lines that extend over a mast of the lift truck to the load handler.
Many types of load handlers have multiple, separately-controllable fluid power functions. Most of these functions require bidirectional, reversible actuation. Examples of such load handlers include side-shifting fork positioners, side-shifting push-pull attachments, side-shifting and/or rotational load clamps having either parallel sliding clamp arms or pivoting clamp arms, and other types of fluid power-actuated multi-function load handlers. Normally, the foregoing types of load handlers are mounted on a load carriage that is selectively raised and lowered on a mast of an industrial lift truck. Multiple fluid control valves in the lift truck operator's compartment may separately regulate each of the multiple fluid power functions of the load handler. In such cases, four or even six hydraulic lines must communicate between the lift truck and the load handler to operate the multiple bidirectional functions. To avoid the necessity for more than two hydraulic lines extending over the mast of the lift truck, it has long been common to provide only a single control valve in the operator's compartment connected to a pair of hydraulic lines extending between the lift truck and a multi-function load handler.
FIGS. 1 and 2, for example, show a lift truck 10 attached to a roll clamp 12 used to clamp and unclamp cylindrical objects such as large paper rolls, using rotatable pivoted arm clamps 14 actuated by hydraulic cylinders 16 and 17. Though FIG. 1 shows only one cylinder 16 and one cylinder 17, the roll clamp 12 may include two cylinders 16 and two cylinders 17, where the cylinders not shown are located behind the cylinders 16 and 17 that are shown. Rotation of the clamps 14 is achieved by a rotator 18, which rotates the clamp bi-directionally about a longitudinal axis in response to a bidirectional hydraulic motor 20. While the roll clamp 12 includes separate cylinders 16 and 17 by which the clamp arms 14 may be independently actuated, some roll clamps have only a single pair of cylinders 16 to actuate one of the clamp arms 14, while the clamp arm 14 not actuated by the cylinders 16 is fixed.
As seen in FIG. 2, hydraulic fluid from a reservoir 24 is exchanged between the lift truck 10 and the roll clamp 12 via two hydraulic lines 26 and 27 that extend over the mast 22 of the lift truck 10. A handle 28 on the lift truck 10 permits an operator to alternately open or close the clamp arms 14 via actuation of the cylinders 16 and 17, and also permits an operator to rotate the clamps 14 in either selected one of a clockwise or counter clockwise direction via a rotator motor 30. A switch 32 located on the handle 28 is used to determine which function (rotation or clamping) is controlled by the handle 28. The switch 32 is integrated into a wireless transmitter 34 that is in communication with a wireless receiver 36 having a corresponding switch 38 in the roll clamp 12. Thus, for example, an operator can wirelessly cause the switch 38 to operate a spring-biased solenoid valve 40 between an open position and a closed position. It should be understood by those of skill in the art that many other operations may be hydraulically enabled, besides opening and closing a clamp, such as raising or lowering a carriage, side-shifting or rolling a carriage, among many other functions common to lift trucks.
In the open position (as depicted in FIG. 2), pressurized fluid is directed from the reservoir 24 in the lift truck 10, through lines 26, 27 and over the mast 22 to operate the rotator motor 30 in either of two rotational directions depending on the position of the handle 28, i.e. by determining the direction of the flow through the lines 26, 27. Conversely, when the operator uses the switch 32 to wirelessly activate the solenoid valve 40, fluid from the reservoir 24 flows through a pilot line 42 to cause selector control valve 44 to redirect fluid from the rotator motor 30 to the clamp cylinders 16 and 17, as shown in FIG. 2. In this configuration, operation of the handle 28 will alternatively extend or retract the cylinders 16 depending on the position of the handle 28, i.e. by determining the direction of the flow through the lines 26, 27. If a third hydraulic function, such as laterally extending the roll clamp frame were also included, a second pilot-operated valve assembly similar to the combination of valves 40 and 44 would be provided for lateral control using an assembly similar to piston and cylinder assemblies 17, together with a second transmitter/receiver set such as 34 and 36, and a second operator-controlled electrical switch 32.
Hydraulically actuated solenoid switches located on remote attachments, such as the valves 40 and 44 shown in FIG. 2, require a non-trivial amount of power to operate—typically more power than can feasibly be transferred by a wireless radio signal. In such cases, one or more solenoid valves are mounted on the load handler and are controlled by electrical wires routed between the lift truck and the load handler, over the mast of the lift truck, so that the operator can electrically select which load handler function will be actuated by the single pair of hydraulic lines. The masts, however, often include rigid metal frames that are slideably engaged with each other to provide a telescoping extension for the mast. Designing a mast having these electrical wires is a complicated task, as there may be bearings between the moving frames and the wires, and the wires must be placed proximate the sliding metal frames without interfering with movement of the mast. Even with the most careful design, routing the electrical wires over the lift truck mast to a movable load handler requires exposure of the wires and their connectors to significant hazards, wear, and deterioration, which results in breakage, short-circuiting, corrosion and other problems that require relatively frequent replacement and downtime. Moreover, lift truck electrical systems range from twelve to ninety volts, requiring a variety of special coils for the solenoid valves.
To eliminate the need for electrical wires that extend over the mast of a lift truck, some load handlers are equipped with a power supply such as a battery to operate the solenoid valves, or other devices that require power, on the load handler. Batteries on attachments, though, deplete rather quickly necessitating replacement and/or frequent charging. This can become quite burdensome and/or inefficient, particularly in energy intensive applications that include multiple batteries on each attachment, where each battery requires weekly replacement or downtime for recharging.
Moreover, when electrical power to hydraulic solenoid valves or other electronic devices is provided by a power supply on the attachment, but controlled by an operator on a lift truck, some means must be used to provide control signals to the attachment-side electrical system to operate the attachment's electrical equipment. Typically, this is performed using wireless communication channels between transmitters on the lift truck and receivers on the attachment, as shown for example in U.S. Pat. Nos. 3,647,255, 3,768,367, 3,892,079, 4,381,872, 4,526,413, and 6,662,881. Though eliminating the need for electrical wires over the mast of a lift truck, wireless transmitters may often clutter the lift trucks, particularly when those lift trucks are to be serially attached to several different types of attachments that have different respective types of electrical components, e.g. solenoid switches, sensor arrays, bar code readers, lasers, etc.
What is desired, therefore, is improved systems and methods for operating electrical and/or electromechanical equipment on remote attachments, such as lift truck load handlers.